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IC 


8959 



Bureau of Mines Information Circular/1983 




Economic and Technical Evaluation 
of the Sulfurous Acid-Caustic 
Purification Process for Producing 
Alumina From Kaolinitic Clay 



By Deborah A. Kramer 



UNITED STATES DEPARTMENT OF THE INTERIOR 



Information Circular 8959 



Economic and Technical Evaluation 
of the Sulfurous Acid-Caustic 
Purification Process for Producing 
Alumina From Kaolinitic Clay 



By Deborah A. Kramer 




UNITED STATES DEPARTMENT OF THE INTERIOR 
James G. Watt, Secretary 

BUREAU OF MINES 
Robert C. Horton, Director 



# 



op 



^\<^. 

# 



Library of Congress Cataloging in Publication Data: 



Kramer, Deborah A 

Economic and technical evaluation of the sulfurous acid-caustic 
purification process for producing alumina from kaolinitic clay. 

(Information circular / United States Department of the Interior, Bu- 
reau of Mines ; 8959) 

Bibliography: p. 11-12. 

Supt. of Docs, no.: I 28.27:8959. 

1. Aluminum oxide. 2. Sulphurous acid. 3. Clay. 4. Leaching. 
I. Title. II. Series: Information circular (United States. Bureau of 
Mines) ; 8959. 



TN295.U4 [TP245.A4] 622s [669'. 722] 83-600303 



CONTENTS 



Page 



Abstract 1 

Introduction 2 

Process description 2 

Clay preparation section 4 

Sulf urous acid leaching section 4 

Sulfite precipitation and decomposition section 4 

Sulfur dioxide handling section. 5 

Caustic digestion section 5 

Trihydrate precipitation and calcination section 6 

Digestion liquor regeneration section 6 

Cost estimate 7 

Capital costs 7 

Operating costs. 9 

Economic and technical discussion 9 

References 11 

Appendix. — Utility requirements, direct labor requirements, daily thermal re- 
quirements, equipment cost summaries, and material balances 13 

ILLUSTRATIONS 

1 . Sulf urous acid digestion and crude alumina production 3 

2 . Caustic purification 3 

A-l. Material balance, clay preparation section 24 

A-2. Material balance, sulfurous acid leaching section..... 24 

A-3. Material balance, sulfite precipitation and decomposition section 24 

A-4. Material balance, sulfur dioxide handling section 25 

A-5. Material balance, caustic digestion section 25 

A-6. Material balance, trihydrate precipitation and calcination section 26 

A-7. Material balance, digestion liquor regeneration section 26 

TABLES 

1 . Composition of the calcined kaolinitic clay (dry basis) 4 

2. Estimated capital cost 7 

3. Estimated annual operating cost 10 

A-l. Raw material and utility requirements 13 

A-2. Direct labor requirements, operators per shift 13 

A-3. Daily thermal requirements 14 

A-4. Major items of equipment 15 

A-5. Equipment cost summary , clay preparation section 16 

A-6. Equipment cost summary, sulfurous acid leaching section 17 

A-7. Equipment cost summary, sulfite precipitation and decomposition section. 18 

A-8. Equipment cost summary, sulfur dioxide handling section 19 

A-9. Equipment cost summary, caustic digestion section 20 

A-10. Equipment cost summary, trihydrate precipitation and calcination section 21 

A-ll. Equipment cost summary, digestion liquor regeneration section 22 





UNIT OF MEASURE ABBREVIATIONS USED IN 


THIS REPORT 


Btu 


British thermal 


unit 




gal/ft 2 «h 


gallon per square foot 
per hour 


Btu/d 


British thermal 


unit 


per 








day 






h 


hour 


Btu/gal 


British thermal 
per gallon 


unit 




h/d 
kW»h 


hour per day 
kilowatt-hour 


Btu/lb 


British thermal 


unit 


per 








pound 






lb 


pound 


°c 


degree Celsius 






Mgal 


thousand gallon 


d/wk 


day per week 






min 


minute 


d/yr 


day per year 






MMBtu 


million British thermal 
unit 


°F 


degree Fahrenheit 
















pet 


percent 


i ft 


foot 






psig 


pound per square inch, 


ft 2 


square foot 








gauge 


gal 


gallon 






ton/d 


short ton per day 


gal/d 


gallon per day 






yr 


year 



ECONOMIC AND TECHNICAL EVALUATION OF THE SULFUROUS ACID-CAUSTIC 

PURIFICATION PROCESS FOR PRODUCING ALUMINA 

FROM KAOLINITIC CLAY 

By Deborah A, Kramer 



ABSTRACT 

An economic and technical evaluation of a proposed process to recover 
alumina by leaching calcined kaolinitic clay with sulfurous acid is pre- 
sented in this Bureau of Mines report. After the insoluble portion of 
the clay has been removed by leaching, monobasic aluminum sulfite is 
precipitated from the pregnant leach solution by partial hydrothermal 
decomposition. Further heating completes the decomposition to an impure 
alumina hydrate. This intermediate is purified in a modified Bayer pro- 
cess, which includes dissolving the alumina hydrate in a caustic solu- 
tion at high temperature and pressure, then decreasing the temperature 
and pressure to precipitate alumina trihydrate. Calcining the trihy- 
drate produces the alumina product. 

A cost estimate was prepared for a plant producing 1,000 tons of alu- 
mina per day, 350 d/yr. The estimated operating cost is approximately 
$475 per ton of alumina. This is substantially higher than a comparable 
estimated operating cost for the Bayer process of $250 per ton of alu- 
mina. The proposed process does not appear economically attractive, even 
as a method to modify a current Bayer processing plant to use a kao- 
linitic clay feed. High capital costs and high energy requirements make 
the process prohibitively expensive. 



1 Chemist, Avondale Research Center, Bureau of Mines, Avondale, MD. 



INTRODUCTION 



The Bureau of Mines is investigating 
technologies for the recovery of alumina 
from domestic nonbauxitic resources. 
Most of the alumina consumed in the 
United States is produced from imported 
bauxite. The United States has very lim- 
ited supplies of bauxite, but has large 
reserves of alumina-containing clay and 
other resources. Development of an eco- 
nomic process to recover the alumina from 
kaolinitic clay or other domestic re- 
sources would insure a continuing alumina 
supply to meet national needs. 

The Bureau of Mines has previously 
evaluated a number of processes for re- 
covering alumina from clay and anortho- 
site. None of these processes appeared 
economically competitive with the Bayer 
process; however, a few warranted further 
investigation because their costs were 
not appreciably higher than those of the 
Bayer process. The technology developed 
by these investigations could prove sig- 
nificant if the cost of imported bauxite 
increases. 

One of these processes involves sulfur- 
ous acid leaching of kaolinitic clay, 
then purification of the crude alumina 
product by a modified Bayer process. Two 
previous evaluations of the sulfurous 
acid process, based on limited data, 



indicated that the proposed process 
appeared economically attractive (1-2). 2 

The sulfurous acid process dates back 
to the late 1800' s. Development was 
attributed to Th. Goldschmidt A.G. This 
process occasioned numerous patents (3- 
10). In 1938, VAWAG at Lippewerk, Ge7- 
many, tried the Goldschmidt process on a 
commercial scale but found that the alu- 
mina product contained an excessive 
amount of impurities. It was then that 
Bayer purification was added to produce a 
cell-grade alumina ( 11 ) . 

In the early 1980' s researchers at the 
Bureau of Mines investigated the sulfur- 
ous acid leaching process on a laboratory 
scale. The objective of this research 
was to expand the experimental data base 
on the process, to confirm assumptions 
used in previous evaluations, and to 
determine if additional investigations in 
the Bureau's miniplant project were war- 
ranted (12). 

The present study includes data (poor 
alumina recoveries, longer leaching time, 
etc.) from the recent Bureau research 
(12) and has been prepared to reassess 
the potential economics and compare the 
results with the previous evaluations. 



PROCESS DESCRIPTION 



In the proposed process, raw kaolinitic 
clay is calcined to convert the contained 
alumina to an acid-soluble form. The 
calcined clay is leached with a sulfurous 
acid solution. Alumina is extracted in 
the form of aluminum sulfite, which is 
separated from the insoluble residue by 
filtration. The temperature and pressure 
of the pregnant leach solution are in- 
creased to precipitate monobasic aluminum 
sulfite. Decomposition of the monobasic 
aluminum sulfite produces an impure alu- 
mina hydrate. 

The impure alumina hydrate is purified 
in a modified Bayer process. First, it 
is dissolved in a caustic solution at 



high temperature and pressure. Undis- 
solved impurities are removed, and alumi- 
na trihydrate is precipitated by cooling 
the solution to the point of supersatura- 
tion, then seeding with fine trihydrate 
crystals. The trihydrate is calcined to 
obtain the final alumina product. A ba- 
sic process flowsheet is shown in figures 
1 and 2 for a plant designed to pro- 
duce 1,000 tons of alumina per day based 
on 3 shifts per day operation, 350 
d/yr. For purposes of discussion, the 
plant is divided into seven major 

^Underlined numbers in parentheses re- 
fer to items in the list of references 
preceding the appendix. 





















Recycle sulfurous acid 


COMPRESSION 






' 


1 










1 


I 






MISTING 


« Water 






1 


1 




V 






m Oust 


CALCINATION 


Calcined _ 


LEACHING 






~~ loss 


clay 












t 


Aluminum 
sulfite 
, slurry 








Leach ^ 
residue 

Recycle 

leach 

solution 




' 








FILTRATION 


S0 2 from leaching 


* 














P 


regnant 
liquor 


4 

1 


Wash water 








PRECIPITATION 


S0 2 from precipitation 
















' 


1 
















THICKENING 




DECOMPOSITION 


Decomposition fc 


CONDENSATION 








* 


* 


vapor 












l 


1 














Waste 


FILTRATION 




1 




solution 








Alu 
monohj 


1 

lina 

drate 







Concentrated S0 2 gas ■ 



Stripping 



ABSORPTION 
1 



Stripped 



SULFUR BURNING 

r 



Air Elemental 

sulfur 



FIGURE 1. - Sulfurous acid digestion and crude alumina production. 



Al umi na 
monohydrate Steam 





1 


i 


1 




Wash water 




gestion residue 




A1 2 3 -3H 2 _ 






DIGESTION 




tf 




' 


' 


\ 


' 




FLASH COOLING 


FILTRATION 




Causti 




i 


k 


1 


' 


< 


Pregnant 
solution 




Filtrate and washings 












i 


f 












PRECIPITATION 




THICKENING 




FILTRATION 
AND WASHING 


CALCINATION 


St'rdTl 






filter cake" 




* See 


d crysta 


Is 






Recyc 
so 

1 


e caustic 




i 


I 


1 




Watery. 








' 




1 




EVAPORATION 




Alumina 


vapor 




Wash water 






Makeu 
reagen 


P . 
ts 
















c leach so 


lution 


1 


1 





FIGURE 2. - Caustic purification. 



sections. The material balances for 
these sections are shown in the appendix. 

CLAY PREPARATION SECTION 

Kaolinitic clay is delivered to the 
plant by truck from a nearby clay pit and 
dumped into a hopper. The clay is then 
conveyed to a covered storage pile con- 
taining a 30-day supply. 

Clay is withdrawn from this pile as 
needed and fed to hammer mills for crush- 
ing to minus 16 mesh. Discharge from the 
hammer mills is conveyed to a pelletizing 
disk, where the clay is misted before 
being fed to surge bins. 

Minus 16-mesh clay is calcined in a 
fluidized bed at 750° C (1,382° F) to 
remove the 18 pet free moisture and the 
combined water. The calcination reac- 
tion, which converts the contained alu- 
mina to an acid-soluble form, is assumed 
to be 

Al 2 3 '2Si0 2 '2H 2 -»- Al 2 3 *2Si0 2 + 2H 2 0. 

Calcined clay is cooled to 65° C 

(150° F) and conveyed to the leaching 
section. The analysis of the calcined 

clay, shown in table 1, was taken from 

the material balance prepared by the 
researchers 
the calcined 



(12). The Si0 2 content of 
clay reported by the re- 
searchers was assumed to include TiOo 



clay. The 
shown sepa- 



known to be present in the 

estimated Ti0 2 content is 

rately in the analysis given in table 1. 

TABLE 1. - Composition of the calcined 
kaolinitic clay, dry basis 



Constituent 



wt pet 



A1 2 3 41.2 

Si0 2 54.4 

Ti0 2 3.1 

Fe 2 3 1.3 

Total 100.0 



SULFUROUS ACID LEACHING SECTION 

Calcined clay is mixed with sulfurous 
acid leach solution and pumped to 12 
trains of 10 pressure-leach tanks. The 
pressure is maintained at 160 psig and 
the temperature at 60° C (140° F) during 
the 17-h leach. Sulfurous acid is in- 
jected into the tanks to maintain a 30- 
pct sulfurous acid solution. Calcined 
clay reacts with sulfurous acid to pro- 
duce aluminum sulfite by the following 
reaction: 

3H 2 S0 3 + Al 2 3 »2Si0 2 

+ A1 2 (S0 3 ) 3 + 2Si0 2 + 3H 2 0. 

Sixty-seven percent of the alumina in the 
clay is assumed to react. 

The leach slurry is pumped to pressure- 
leaf filters where the solids are sepa- 
rated from the pregnant liquor at a rate 
of 3.8 gal/ft 2 »h and washed. The filter 
cake is dumped from the filters into 
sumps, where the solids are reslurried, 
neutralized with slaked lime, and then 
pumped to a tailings pond. Filtrate and 
washings are combined in a surge tank and 
pumped to the sulfite precipitation and 
decomposition section. Due to the 
pressure drop during filtration, a por- 
tion of the sulfurous acid decomposes to 
form sulfur dioxide. This vapor is col- 
lected as it is blown off from the fil- 
trate receiving vessels and sent to the 
sulfur dioxide handling section. 

SULFITE PRECIPITATION AND DECOMPOSITION 
SECTION 

Pregnant liquor from leaching is pumped 
to autoclaves that operate at 110° C 
(230° F) and 60 psig. Under these condi- 
tions, aluminum sulfite precipitates as 
monobasic aluminum sulfite by the follow- 
ing reaction: 

A1 2 (S0 3 ) 3 + 5H 2 ->- A1 2 3 «2S0 2 '5H 2 + S0 2 . 



Ninety-four percent of the aluminum sul- 
fite decomposes in 2 h. Sulfur dioxide 
formed during the reaction is vented and 
sent to the sulfur dioxide handling sec- 
tion. The exiting hot slurry is depres- 
surized, partially cooled by preheating 
the incoming solution in heat exchangers, 
and then pumped to a thickener. Overflow 
from the thickener is recycled to the 
sulfurous acid leach tanks. Underflow, 
consisting of a 19-pct monobasic aluminum 
sulfite slurry, is pumped to a second set 
of autoclaves operating at 150° C 
(302° F) and 50 psig. At this tempera- 
ture and pressure, the monobasic aluminum 
sulfite will further decompose to form 
alumina monohydrate by the following 
reaction: 

A1 2 3 »2S0 2 »5H 2 

+ A1 2 3 'H 2 + 2S0 2 + 4H 2 0. 

Decomposition requires a 1-h residence 
time in the reactors. 

Sulfur dioxide and water vapor that are 
produced and vented during decomposition 
are collected and sent to the sulfur 
dioxide handling section. All sulfur 
dioxide process losses are included with 
the decomposition vapor in the material 
balance. Exiting hot slurry is used to 
preheat the autoclave feed and then 
pumped to rotary-vacuum drum filters. 
The alumina monohydrate filter cake is 
conveyed to the caustic digestion sec- 
tion. Filtrate from the drum filters 
is reslurried with the leach residue 
and pumped to the tailings pond for 
neutralization. 

SULFUR DIOXIDE HANDLING SECTION 

Makeup sulfur dioxide is produced by 
burning liquid sulfur. This process 
forms a hot gas containing approximately 
19 pet sulfur dioxide. The gas is par- 
tially cooled in a waste-heat boiler and 
then passed through an absorption tower, 
where the sulfur dioxide is absorbed by 
water. This weak sulfurous acid solution 
is then passed through a stripping tower, 
where most of the water is removed to 



produce a concentrated sulfur dioxide gas 
stream. Stripping wastes are used to 
reslurry the process residues for dis- 
posal in the tailings pond. 

Mixed sulfur dioxide and water vapors 
produced in the sulfite precipitation and 
decomposition section are concentrated by 
removing some of the water through con- 
densation. This vapor is combined with 
the concentrated makeup sulfur dioxide 
gas stream and the two sulfur dioxide- 
rich gas streams recovered from leaching 
and sulfite precipitation. The combined 
streams are compressed to form a strong 
sulfurous acid and recycled to the leach 
tanks. 

CAUSTIC DIGESTION SECTION 

To remove excessive quantities of im- 
purities from the crude decomposition 
product, the filter cake is processed by 
a modified Bayer process. Caustic solu- 
tion is mixed with the alumina monohy- 
drate filter cake and pumped into 
pressure-digestion vessels. Steam is 
injected directly into these tanks to 
maintain the operating condition of 
230° C (446° F) and 400 psig (L3). Alu- 
mina monohydrate reacts in the following 
manner: 

A1 2 3 «H 2 + 2NaOH ■> 2NaAl0 2 + 2H 2 0. 

Ninety-eight percent of the alumina mono- 
hydrate is dissolved during the 30-min 
retention time. 

The slurry is exposed to air containing 
carbon dioxide in open tanks and thicken- 
ers, and by the air-lift agitators used 
in the precipitation tanks. This causes 
some of the caustic to react to form 
sodium carbonate. Since sodium carbonate 
does not dissolve alumina, lime is added 
in the digestion liquor regeneration sec- 
tion to react with the sodium carbonate 
and regenerate the caustic solution by 
forming insoluble calcium carbonate by 
the following reaction: 

Ca(0H) 2 + Na 2 C0 3 ->- CaC0 3 + 2NaOH. 



Slurry exiting the digestion tanks is 
depressurized and cooled in a series of 
nine flash tanks. Steam is recovered 
from the flash tanks at the pressures 
shown in the material balance, and used 
to preheat the caustic leach solution. 
Cooled slurry is filtered, and the solids 
are washed, reslurried, and pumped to the 
tailings pond for neutralization. Fil- 
trate and washings are combined and 
pumped to the trihydrate precipitation 
and calcination section. 

TRIHYDRATE PRECIPITATION 
AND CALCINATION SECTION 

Pregnant solution from the caustic 
digestion section is pumped to 30 pre- 
cipitation tanks, 30 ft in diameter by 64 
ft in height, which are equipped with air 
lifts for agitation. Seed alumina trihy- 
drate crystals are fed to the precipita- 
tion tanks in an amount equivalent to 
100 pet of the alumina trihydrate pre- 
cipitated. Seeding the supersaturated 
solution precipitates alumina trihydrate 
by the following reaction: 

2NaA10 2 + 4H 2 -*- A1 2 3 »3H 2 + 2NaOH. 

Forty hours are allowed for 
precipitation. 

The slurry from precipitation is pumped 
to a series of three thickeners. Coarse 
alumina trihydrate crystals are recovered 
in the underflow from the primary thick- 
ener. They are filtered, washed, and fed 
to a fluidized-bed calciner. In the cal- 
ciner, alumina trihydrate is converted to 
alumina by the following reaction: 



A1 2 3 



3H 2 ->- A1 2 3 + 3H 2 0, 



This reaction occurs at 950° to 
1,050° C (1,740° to 1,920° F). The 
cooled alumina product is conveyed to 
silos with a 60-day capacity for storage 
and shipment. 



Filtrate and washings from the calciner 
filters are combined with overflow from 
the primary thickener and pumped to a 
secondary thickener. Overflow from this 
thickener is sent to a tertiary thick- 
ener. The clarified overflow from the 
tertiary thickener is pumped to the 
digestion liquor regeneration section. 
Underflows from both the secondary and 
tertiary thickeners are combined and 
recycled to the precipitation tanks to 
provide the alumina trihydrate seed 
crystals. 

DIGESTION LIQUOR REGENERATION 
SECTION 

Clarified solution from the tertiary 
thickener in the trihydrate precipitation 
and calcination section is concentrated 
in a five-effect evaporator and pumped to 
storage tanks. A bleed stream is pumped 
from the storage tank to a single-effect 
evaporator. Further concentration of the 
bleed stream allows for removal and con- 
trol of minor impurities and organic com- 
pounds, which build up in the process 
stream. Water vapor is condensed and 
returned to the storage tanks along with 
the purified bleed stream. 

Concentrated solution is pumped to a 
mixing tank where makeup caustic and lime 
are added. This solution is preheated 
using steam recovered from flash-cooling 
the digestion liquor and recycled to the 
digestion tanks. 

Equipment has been provided for clean- 
ing and descaling the heat exchangers 
used throughout the process. This equip- 
ment consists of tanks to store the solu- 
tion removed from the heat exchangers, 
tanks containing a sulfuric acid cleaning 
solution, and tanks for the spent clean- 
ing solution, as well as the necessary 
pumps and feed tanks. 



COST ESTIMATE 

The cost estimate presented in this cost for the plant described. Although 

report is based on laboratory data from the degree of confidence in any specific 

the Bureau of Mines (12) and Bayer pro- study estimate is not great with respect 

cess data from published and nonpublished to the actual cost, greater confidence is 

sources. justified when comparing a group of simi- 
lar processes evaluated by identical 

CAPITAL COSTS methods. 

The capital cost estimate is of the The estimated fixed capital cost on a 

general type called a study estimate by fourth quarter 1982 basis (Marshall and 

Weaver and Bauman (14). This type of Swift (M and S) index of 749.3) of a 

estimate, prepared from a flowsheet and a plant producing 1,000 tons of alumina per 

minimum of equipment data, can be ex- day is about $752 million, as shown in 

pected to be within 30 pet of the actual table 2. This is equivalent to a cost of 

TABLE 2. - Estimated capital cost 1 

Fixed capital: 

Clay preparation section $46,084,000 

Sulfurous acid leaching section 255,061,600 

Sulfite precipitation and decomposition section 40,371,600 

Sulfur dioxide handling section 11 , 008 ,500 

Caustic digestion section 18,205,100 

Trihydrate precipitation and calcination section 36,828,900 

Digestion liquor regeneration section 24 ,685 ,600 

Tailings pond 5 ,879,400 

Steamplant 30,895,600 

Subtotal 469 ,020, 300 

Plant facilities, 10 pet of above subtotal 46,902,000 

Plant utilities, 12 pet of above subtotal 56,282,400 

Total plant cost 572,204,700 

Land cost 

Subtotal 572,204,700 

Interest during construction period 135,366,800 

Fixed capital cost 707,571,500 

Working capital: 

Raw material and supplies 1,283,800 

Product and in-process inventory 13,686, 000 

Accounts receivable 13,686,000 

Available cash 8,738,200 

Working capital cost 37,394,000 

Capitalized startup costs 7,075,700 

Subtotal 44,469,700 

Total capital cost 752,041,200 

1 Basis: M and S equipment cost index of 749.3. 



about $2,000 per annual ton of product. 
The plant is designed to operate 3 shifts 
per day, 7 d/wk, 350 d/yr, except for 
some of the clay receiving facilities, 
which operate 2 shifts per day, 5 d/wk, 
and the clay crushing facilities, which 
operate 2 shifts per day, 7 d/wk. 

Equipment costs for the proposed pro- 
cess are based on cost-capacity data and 
manufacturers' cost quotations. Cost 
data are brought up to date by the use of 
inflation indexes. Capital costs for the 
f luidized-bed flash calciner are based on 
a paper by Lussky (15). The tailings 
pond is designed as a lined pond with a 
2-yr life. It is assumed that after 2 
yr, the mine site will be developed to 
dispose of the remainder of the process 
residue as backfill. In developing the 
plant capital costs, corrosion-resistant 
materials of construction were used where 
appropriate. For example, the leach 
tanks are constructed of stainless steel 
to withstand the acid environment. 

Factors for piping, etc. , except for 
the foundation and electrical factors, 
are assigned to each section, using as a 
basis the effect fluids, solids, or a 
combination of fluids and solids may have 
on the process equipment. The foundation 
factor is estimated for each piece of 
equipment individually, and a factor for 
the entire section is calculated from the 
totals. The electrical factor is based 
on the motor horsepower requirements for 
each section. A factor of 10 pet, re- 
ferred to as miscellaneous, is added to 
each section to cover minor equipment and 
construction costs that are not shown 
with the equipment listed. 

For each section, the field indirect 
cost, which covers field supervision, 
inspection, temporary construction, 
equipment rental, and payroll overhead, 
is estimated at 10 pet of the direct 
cost. Engineering cost is estimated at 
10 pet, and administration and overhead 
cost is estimated at 5 pet of the con- 
struction cost. A contingency allowance 
of 15 pet and a contractor's fee of 5 pet 
are included in the section costs. 



The costs of plant facilities and plant 
utilities are estimated as 10 and 12 pet, 
respectively, of the total process sec- 
tion costs and include the same field 
indirect costs, engineering, administra- 
tion and overhead, contingency allowance, 
and contractor's fee as are included in 
the section costs. Included under plant 
facilities are the costs of material and 
labor for auxiliary buildings such as 
offices, shops, laboratories, and cafe- 
terias, and the cost of nonprocess equip- 
ment such as office furniture, and 
safety, shop, and laboratory equipment. 
Also included are labor and material 
costs for site preparation such as clear- 
ing, grading, drainage, roads, and 
fences. The costs of water, power, and 
steam distribution systems are included 
under plant utilities. 

The cost for interest on the capital 
borrowed for construction is included as 
interest during construction, assuming an 
interest rate of 11 pet. To determine 
the interest cost during construction, 
the total plant cost is factored by 
an adjusted interest rate, which de- 
pends upon the length of the construction 
period and the interest rate at which 
the money is borrowed. Cost for the 
plant owner's supervision is not included 
in the capital cost of the proposed 
plant. 

Working capital is defined as the funds 
in addition to fixed capital, land in- 
vestment, and startup costs that must be 
provided to operate the plant. Working 
capital, also shown in table 2, is esti- 
mated from the following items: (1) Raw 
material and supplies inventory (cost of 
raw material and operating supplies for 
30 days), (2) product and in-process 
inventory (total operating cost for 30 
days), (3) accounts receivable (total 
operating cost for 30 days), and (4) 
available cash (direct expenses for 
30 days). 

Capitalized startup costs are estimated 
as 1 pet of the fixed capital, which is 
shown in table 2. 



OPERATING COSTS 

The estimated operating costs are based 
on the average of 350 d/yr of operation 
over the life of the plant. This allows 

15 days' downtime per year for inspec- 
tion, maintenance, and unscheduled inter- 
ruptions. The operating costs are 
divided into direct, indirect, and fixed 
costs. 

Direct costs include raw materials, 
utilities, direct labor, plant mainten- 
ance, payroll overhead, and operating 
supplies. The raw material costs do not 
include transportation costs because the 
plant is assumed to be located adjacent 
to the clay pit. Electricity, water, 
fuel oil, and coal are purchased utili- 
ties. The temperature of the water from 
the cooling tower is assumed to be 32° C 
(90° F). Raw material and utility re- 
quirements per ton of alumina are shown 
in table A-l (appendix). 

The direct labor assignments are shown 
by sections in table A-2. The direct 
labor cost is estimated on the basis of 
assigning 4.2 employees to each position 
that operates 24 h/d, 7 d/wk and 2.8 
employees to each position that operates 

16 h/d, 7 d/wk. The cost of labor super- 
vision is estimated as 15 pet of the 
labor cost. 

Plant maintenance is separately esti- 
mated for each piece of equipment and for 



the buildings, electrical system, piping, 
plant utility distribution systems, and 
plant facilities. 

Payroll overhead, estimated as 35 
pet of direct labor and maintenance 
labor, includes vacation, sick leave, 
social security, and fringe benefits. 
The cost of operating supplies is esti- 
mated as 20 pet of the cost of plant 
maintenance. 

Indirect costs are estimated as 40 pet 
of the direct labor and maintenance 
costs. The indirect costs include the 
expenses of control laboratories, ac- 
counting, plant protection and safety, 
plant administration, marketing, and com- 
pany overhead. Research and overall 
company administrative costs outside the 
plant are not included. 

Fixed costs include the cost of taxes 
(excluding income taxes), insurance, and 
depreciation. The annual costs of both 
taxes and insurance are each estimated as 
1 pet of the plant construction cost. 
Depreciation is based on a straight-line, 
20-yr period. 

The estimated annual operating cost, 
shown in table 3, for a plant producing 
1,000 tons of alumina per day is about 
$166 million, or $475 per ton of alumina 
product. 



ECONOMIC AND TECHNICAL DISCUSSION 



From the cost estimate presented in 
this report, the proposed process does 
not appear to be an economically competi- 
tive method for producing alumina. The 
operating cost of $475 per ton of alumina 
vastly exceeds the estimated operating 
cost of about $250 per ton of alumina for 
the Bayer process (16). 

Costs for utilities, mainly electric 
power and coal for producing steam, 
account for over 30 pet of the total 
operating cost. Total steam requirements 
for this process are over 19 billion 
Btu/d, which is equivalent to almost 



24,000 lb of steam per ton of alumina. 
Sulfite precipitation and decomposition 
are responsible for 72 pet of this steam 
requirement. Most of the electric power 
required is utilized in the leach tanks 
and the sulfur dioxide compressors. The 
slurry in the leach tanks must be contin- 
ually agitated during the 17-h retention 
time, and with the large number of leach 
tanks necessary, this operation consumes 
an inordinate amount of electric power. 
Compressors require a large amount of 
electricity to compress over 12,000 ton/d 
of sulfur dioxide gas. 



10 



TABLE 3. - Estimated annual operating cost 



Annual 
cost 



Cost 
per ton 
alumina 



Direct cost: 
Raw materials: 

Kaolinitic clay at $3 per ton 

Lime at $31.25 per ton 

Sodium hydroxide, 50-pct at $175 per ton. 

Sulfur at $114.75 per ton , 

Limestone at $4 per ton , 

Chemicals for steamplant water treatment, 
Total , 



Utilities: 

Electric power at $0,032 per kW'h, 
Process water at $0.25 per Mgal... 

Coal at $45 per ton , 

Heavy oil at $1 per gallon , 

Total , 



Direct labor: 

Labor at $9 per hour , 

Supervision, 15 pet of labor, 
Total 



Plant maintenance: 

Labor , 

Supervision, 20 pet of maintenance labor. 

Materials 

Total , 



Payroll overhead, 35 pet of above payroll , 

Operating supplies, 20 pet of plant maintenance, 



Total direct cost, 



Indirect cost, 40 pet of direct labor and maintenance, 

Fixed cost: 

Taxes, 1 pet of total plant cost , 

Insurance, 1 pet of total plant cost , 

Depreciation, 20-yr life 



Total operating cost, 



$5,616,500 

273,400 

1,041,300 

2,128,600 

112,000 

547,400 



9,719,200 



12,108,100 

668,600 

30,835,300 

6,634,000 



50,246,000 



3,425,800 
513,900 



3,939,700 



13,408,900 

2,681,800 

13,408,900 



29,499,600 



7,010,600 
5,899,900 



106,315,000 
13,375,700 



5,722,000 

5,722,000 

35,378,600 



166,513,300 



$16.05 

.78 

2.98 

6.08 

.32 

1.56 



27.77 



34.59 

1.91 

88.10 

18.95 



143.55 



9.79 
1.47 



11.26 



38.31 

7.66 

38.31 



84.28 



20.03 
16.86 



303.75 



38.22 



16.35 

16.35 

101.08 



475.75 



The estimated capital cost for the pro- 
posed plant is very high, resulting in 
high depreciation costs. In this esti- 
mate, depreciation accounts for about 20 
pet of the operating costs. Basically, 
all the tanks and filters necessary for 
the process are high-capital-cost items. 
However, the largest equipment cost items 



are the leach tanks, the pressure-leaf 
filters, and the sulfite precipitation 
tanks in decreasing order. Because of 
the long retention time, a large number 
of leach tanks is necessary. Each tank 
must be designed to withstand the leach 
pressure and be constructed of stainless 
steel to withstand the acid environment. 



11 



A large number of pressure-leaf filters 
is necessary because of the poor filtra- 
tion rate of the leach residue. 

Originally it had been assumed that the 
sulfurous acid technology could be used 
to produce an alternate feed for an 
existing Bayer plant. The use of an 
existing Bayer plant could reduce the 
capital investment required for recover- 
ing alumina from domestic clay by about 
20 pet, compared with that required for a 
totally new plant. (This does not in- 
clude the extra capital required to mod- 
ify the existing Bayer plant to enable it 
to accept the crude alumina from the sul- 
furous acid plant.) Direct operating 
costs for a totally new plant or a modi- 
fied plant will be similar. Therefore, 
the only operating cost advantage will be 
in reduced depreciation charges. Reduc- 
ing depreciation costs by 20 pet is not 
sufficient to allow the crude alumina 
produced by the sulfurous acid process to 
compete with bauxite as feed to a Bayer 
plant. 

The sulfurous acid leaching process was 
originally investigated because of the 
previously estimated low cost and rela- 
tive ease of recovery of sulfur dioxide 
as a reagent, and because it would pro- 
vide a feed suitable for use in a Bayer 
process. A suitable feed for the Bayer 
process has not been obtained in the 



laboratory with respect to impurity lev- 
els. In previous evaluations, it was 
assumed that the crude alumina would be 
soluble at atmospheric pressure, but 
since it must be pressure-leached, the 
cost of the process has escalated. 

One of the assumptions made necessary 
in preparing this evaluation is that an 
alumina product of cell-grade purity can 
be obtained. This has not been demon- 
strated in the laboratory. The small- 
scale studies have concentrated on the 
sulfurous acid leaching and sulfite pre- 
cipitation and decomposition steps with 
only minimal investigation of the caustic 
digestion step in the Bayer process. 
Research on sulfurous acid leaching in 
the laboratory did not produce a product 
with a low enough sulfur content to meet 
cell-grade specifications. 

In previous evaluations, the process 
was judged to be economically competitive 
with current practices. Recent Bureau of 
Mines research on the sulfurous acid pro- 
cess determined that a longer leaching 
time was required, and that alumina 
extraction was poorer than anticipated 
(67 pet as compared to 80 pet, which was 
previously assumed based on work with 
German clay ( 11 ) ) . In light of the new 
data, this process has become more costly 
and therefore does not appear econom- 
ically competitive. 



REFERENCES 



1. Bengtson, K. B., P. Chuberka, L. E. 
Malm, A. E. McLaughlin, R. F. Nunn, and 
D. L. Stein. Alumina Process Feasibility 
Study and Preliminary Pilot Plant Design. 
Task I Final Report. Comparison of Six 
Processes. BuMines OFR 18-78, 1977, 
253 pp.; NTIS PB 286 638/AS. 

2. Peters, F. A. , P. W. Johnson, and 
R. C. Kirby. Methods for Producing Alu- 
mina From Clay — An Evaluation of the Sul- 
furous Acid-Caustic Purification Process. 
BuMines RI 5997, 1962, 21 pp. 



3. Buche, K. , and H. Ginsberg (as- 
signed to Th. Goldschmidt Corp. , New 
York). Solubilizing Claylike Minerals. 
U.S. Pat. 2,267,490, Dec. 23, 1941. 

4. Fulda, W. , E. Wiedbrauck, and K. 
Buche (assigned to Th. Goldschmidt A. G. , 
Essen, Germany). Process for the Recovery 
of Aluminum Compounds From Aluminiferous 
Minerals. U.S. Pat 2,123,650, July 12, 
1938. 



12 



5. Fulda, W. , E. Wiedbrauck, and K. 
Buche (assigned to Th. Goldschmidt Corp. , 
New York). Manufacture of Monobasic 
Aluminum Sulphite. U.S. Pat. 2,243,060, 
May 20, 1941. 

6. Fulda, W. , E. Wiedbrauck, and R. 
Wittig (assigned to Vereinigte Aluminium- 
Werke Aktiengesellschaf t and Th. Gold- 
schmidt A.-G. , Essen, Germany). Method 
of Producing Pure Alumina. U.S. Pat. 
2,021,546, Nov. 19, 1935. 

7. Fulda, W. , W. Wrigge, and H. Loge- 
mann (assigned to Th. Goldschmidt Corp. , 
New York). Separating Sulphurous Acid 
From Aluminum Sulphites. U.S. Pat. 
2,261,113, Nov. 4, 1941. 

8. Staufer, R. , and K. Konopicky 
(assigned to Alterra A. G. , Luxemburg). 
Process for Treating Argillaceous Mate- 
rial. U.S. Pat. 1,956,139, Apr. 24, 
1934. 



Process for the Decomposition of Sili- 
ceous Aluminous Minerals. U.S. Pat. 
2,006,851, July 2, 1935. 

11. Anderson, R. J. The German Alu- 
minum Industry. Min. Mag., v. 62, 1940, 
pp. 274-284. 

12. Raddatz, A. E., J. M. Gomes, and 
M. M. Wong. Laboratory Investigation of 
a Sulfurous Acid Process for Preparing 
Alumina From Kaolin. BuMines RI 8533, 
1981, 15 pp. 

13. Gerard, G. V., and P. T. Stroup. 
Extractive Metallurgy of Aluminum. In- 
terscience, New York, v. 1, 1963, 355 pp. 

14. Weaver, J. B., and H. C. Bauman. 
Cost and Profitability Estimation. Sec. 
25 in Perry's Chemical Engineers' Hand- 
book, ed. by R. H. Perry and C. H. 
Chilton. McGraw-Hill, 5th ed. , 1973, 
p. 46. 



9 . Wiedbrauck , E . , and K. Buche 
(assigned to Th. Goldschmidt A.-G. , 
Essen-Ruhr, Germany). Process for the 
Production of Monobasic Aluminum Sul- 
phite. U.S. Pat. 1,971,668, Aug. 28, 
1934. 

10. . (assigned to Th. Gold- 
schmidt A.-G., Essen-Ruhr, Germany). 



15. Lussky, E. W. Experience With 
Operation of the Alcoa Fluid Flash Cal- 
ciner. Light Metals, 1980, pp. 69-79. 

16. Kramer, D. A., and F. A. Peters. 
A Cost Estimate of the Bayer Process for 
Producing Alumina — Based on 1982 Equip- 
ment Prices. BuMines IC 8958, 1983. 



13 



APPENDIX. —UTILITY REQUIREMENTS, DIRECT LABOR REQUIREMENTS, DAILY THERMAL 
REQUIREMENTS, EQUIPMENT COST SUMMARIES, AND MATERIAL BALANCES 



Raw material and utility requirements 
per ton of alumina are shown in table A- 
1 , and direct labor requirements and 
daily thermal requirements for each sec- 
tion are shown in tables A-2 and A-3, 
respectively. Major items of equipment 
for each section are shown in table A-4. 
The equipment cost summaries for each 
section in the process are contained in 

TABLE A-l. - Raw material and utility 
requirements 

Quantity 
per ton 
alumina 



Raw materials, tons: 

Kaolinitic clay 

Lime 

Sodium hydroxide, 50-pct. , 

Sulfur 

Limestone 

Utilities: 

Electric power kW*h, 

Process water Mgal. 

Coal tons . 

Heavy oil gal. 



5.349 
.025 
.017 
.053 
.080 



1,081.085 

7.641 

1.958 

18.954 



tables A-5 to A-ll. Material balances 
are shown for each section in figures A-l 
to A-7. 

TABLE A-2. - Direct labor requirements, 
operators per shift 



Section 



Clay preparation section 

Sulfurous acid leaching 
section 

Sulfite precipitation 
and decomposition 
section 

Sulfur dioxide handling 
section 

Caustic digestion 
section 

Trihydrate precipitation 
and calcination section 

Digestion liquor regen- 
eration section 

Steamplant 

General plant 

Total 



Shifts per week 



TIT 



4 
14 

4 

1 

3 

2 

2 
11 





41 



x 3 shifts per day, 7 d/wk. 
2 2 shifts per day, 7 d/wk. 
3 1 shift per day, 5 d/wk. 



^1T 



^5 



14 



TABLE A-3. - Daily thermal requirements 



Section and item 


Steam, 
MMBtu 


Heavy 

oil, 

MMBtu* 


Coal, 
MMBtu 2 


Cooling 
water, 
Mgal 


Clay preparation section: 



128 






9,870 



o 









128 







9,870 



o 




65,971 


Sulfite precipitation and 
decomposition section: 


8,295 
5,644 










o 




o 








13,939 











Sulfur dioxide handling section: 


-295 

41 













o 




o 




14,135 




-254 








14,135 


Caustic digestion section: 


751 
845 
2,207 
-495 
-437 
-510 
-961 
-999 
-560 
-525 
-513 
-349 






























o 




o 




o 




o 


Flash tank 2 


o 




o 




o 




o 




o 




o 




o 


Flash tank. 9 


o 








-1,546 




2,900 






o 


Trihydrate precipitation and calcination 


o 






Digestion liquor regeneration section: 


1,549 
182 
437 
495 
349 
513 
525 
560 
999 
961 
510 































3,379 




408 





























o 




89 




7,080 









40 


3,876 









19,347 
-19,347 


2,900 



9,910 
39,035 


83,982 












2,900 


48,945 


3,982 


Canity of heavy oil (153,000 Btu/gal) = 18,954 gal/d. 
^Quantity of coal (12,500 Btu/lb) = 1,958 ton/d. 











TABLE A-4. - Major items of equipment 



15 



Section and item 

Clay preparation section: 

Hammer mills , 

Felletizing disks 

Fluidized-bed calciners 

Sulfurous acid leaching section: 

Leach tanks , 

Pressure-leaf filters. , 

Sulfite precipitation and decomposition section: 

Precipitation tanks , 

Thickener 

Decomposition tanks 

Sulfur dioxide handling section: 

Absorption tower. 

Stripping tower , 

Caustic digestion section: 

Digestion tanks 

Pressure-leaf filters 

Trihydrate precipitation and calcination section: 

Precipitation tanks , 

Primary thickeners , 

Secondary thickeners , 

Tertiary thickeners , 

Fluid-flash calciner , 

Digestion liquor regeneration section: 

Multief f ect evaporator , 

Evaporator , 



Unit size 



60 by 48 in. 
12-ft diam. 
1,500 ton/d. 



15-ft diam by 45 ft. 
1,645 ft 2 . 



15-ft diam by 45 ft. 

76-ft diam. 

15-ft diam by 45 ft. 



5.9-ft diam by 22.7 ft, 
4.6-ft diam by 19.8 ft, 



12-ft diam by 36 ft, 
1,644 ft 2 . 



30-ft diam by 64 ft, 

27-ft diam. 

59-ft diam. 

1 15-ft diam. 

2.9 billion Btu/d. 



15,699 ft 2 /effect. 
1,519 ft 2 /effect. 



16 



TAbLE A-5 .-Equi pment cost summary* clay preparation section 



Item 



Equipment 



CostU) 



Labor 



Total 



Apron feeder 

Belt conveyor •••• • 

Belt conveyor,.. ,. 

Keclaimer feeders. 

belt conveyor, 

Hoppers 

Apron feeders., 

Hammer mills 

Belt conveyor.,.,.. 

Belt conveyor... 

Storage bin 

Apron feeder... 

Belt conveyor 

Pelletizing disks 

Screw feeders. 

Coal preparation equipment 
Bag dust collectors,.,,,.. 
Screw f eede rs ............ • 

Total , 

Unloading hopper.......... 

F 1 ui di zed-bed calciners... 
Lime scrubber............. 

Front-eno loaders 



208 

671 
1746 

313 

1964 

97 

23b 
5126 

133 

634 
2261 

174 

467 
6012 

121 
3623 

316 
67 



00. 

00, 

00. 

00. 

00, 

00. 

00. 

00. 

00. 

00. 

00. 

00. 

00. 

00. <| 

00. 

00. 

00. 

00. 



2440600, 



Total equipment cost x factor indicated: 

Foundations* x .157 

Buildings* x .563,. 

Structures* x ,100..., , 

Instrumentation* x ,060.,,.,,,,.,,,,,, 

Electrical* x .164 , , 

Piping* x .200 

Painting* x ,020 

Miscellaneous* x ,100 

Total 



Total di rect cost 



Field indirect* 10,0 pet of total direct cost 
Total construction cost, 



3100. 
13300. 
33400. 

4700. 

35600. 

600. 

3500. 
71800. 

2500. 
12700. 
44500, 

2600. 

6600. 

3600. 

1800. 

34900. 

500, 

1300. 



23900. 

80400, 
208000. 

36000. 
234200. 

10500. 

27000. 
584400. 

15800. 

76100. 
270600. 

20000. 

53300, 
604800, 

13900. 
417200, 

32100. 

10000. 



277400. 



2718200. 

(2) 17900. 

(2)20931300. 

(2) 2938600. 

136200, 



382000, 
1375000. 
244100. 
195300. 
450100. 
488200, 
48800. 
244100. 



3427600. 



30169800. 
3017000. 



Engineering* 10.0 pet of total construction cost 
Aami ni st rat i on and overhead* 5,0 pet of total 

construction cost. 

Suototal.. • 



33166800. 
3318700. 
1659300. 



Contingency* 15.0 pet of above subtotal 
Subtotal 



38164800. 
5724700. 



Contractor's fee* 5.0 pet of above subtotal 
Section cost 



43889500. 



2194500. 



46084000. 



(1) Equipment costs are based on the M end S index of 749.3. 

(2) Instal 1 ed cost . 



17 



TABLE A-6 .-Equi pment cost summary, sulfurous acid leachinc section 



Item 



Equ i pment 



costcn 



Labo'p 



Total 



Belt conveyor........ 

Belt conveyor 

Storage bins 

Screw feeders 

Mixing tanks.... 

Pumps. • 

Leach tanks 

Pressure- 1 eaf filters 

Pumps. 

Sumps........... 

Pumps. 

Hoppers.. •••• 

Belt conveyors....... 

Total 



* 



12300. 
12200 0. 
575600. 

37200. 

17 2 0. 

261500. 

73939700. 

5207500. 

67800. 
210700, 
155000: 

19600. 
281100. 



81062200. 



Total equipment cost x factor inoicated: 

Foundations, x .049 

buildings, x .010 ,. 

Structures, x .100,. 

Insulation, x .011............ 

Instrumentation, x .180... 

Electrical, x .020 

Piping, x .500 

Painting, x .080... 

Miscellaneous, x .100 

Total 



Total di rect cost 



Field inoirect, 10.0 pet of total direct cost 
Total construction cost.. • 



2200. 

22300. 

117000. 

5600. 

34900. 

34100. 

184300. 

312900. 

23600. 

44900. 

35900. 

6800. 

65400. 



889900. 



Engineering, 10.0 pet of total construction cost 
Administration and overheaa, 5.0 pet of total 

construction cost.,...,.,. 

Subtotal 



Contingency, 15.0 pet of above subtotal 
Subtotal,., 



Contractor's fee, 5.0 pet of above subtotal 
Section cost 



1450 0. 
144300. 
692600. 

4280 0. 

206900. 

295600. 

7^124000. 

5520400. 

914 0. 
255600. 
190900. 

26600. 
346500. 



81952100. 



3944100. 

774600. 

8106200. 

895000. 

14591200. 

1595600. 

40531100. 

6465000. 

8106200. 



85029000. 



166981100. 
16698100. 



183679200. 

18367900. 

9184000. 



211231100. 

31684700. 



242915800. 
12145800. 



255061600. 



(1) Equipment costs are Dased on the N' and S index of 749.3. 



18 



TABLE A-7 . -Equi pment cost summary* 
sulfite precipitation ana decomposition section 



I tern 



Equi pment 



costm 



Labor 



Total 



Precipitation tanks 

Blowdown tanks..... 

Heat exchangers. • 

Thickener., ...... .......... 

Overflow pumps 

Underflow pumps 

Decomposition tanks........ 

Blowdown tanks... 

Heat exchangers... 

Pumps. 

Rotary- vacuum arum filters. 

Pumps ••...•••••••.•••• 

Reslurry tanks 

Pumps ..................... . 

Sulfur oioxiae storage tank 

Total 

Cooling tower 



$ 3153600 

46300 

1003200 

459500 

24100 

39100 

912300 

21200 

262900 

62400 

4443200 

98700 

121300 

102900 

319400 



22300. 
23700. 
31400. 
30000. 

4700. 

500Q. 

7000. 

9500. 

8700. 
11900. 
222200. 
26300. 
23500. 
21000. 

1100. 



3175900. 

70000. 

1034600. 

489500. 

28800, 

44100. 
919300, 

30700. 
271600. 

74300. 
4665400. 
125000. 
144800, 
123900. 
320500. 



11070100 



448300. 



11518400. 
(2) 1886400. 



Total equipment cost x factor inaicateo; 

Foundations, x .093 

buildings/ x .029 

Structures, x ,100 , 

Insulation/ x .062., 

Instrumentation, x ,180.,,,. 

Electrical/ x .034 

Piping, x .500 

Painting/ x .060 

Miscellaneous/ x .100 ,. 

Total 



1024300 

318200 
1107000 

684400 
1992600 

371000 
5535100 

885600, 
1107000 



13025200 



Total di rect cost 



Field indirect/ 10.0 pet of total direct cost 
Total construction cost • 



26430000. 



2643000. 



Engineering/ 10.0 pet of total construction cost 
Administration and overhead/ 5.0 pet of total 

construction cost. 

Subtotal ••••. 



29073000. 
2907300. 
1453700. 



Contingency/ 15.0 pet of above subtotal 
Subtotal , 



33434000. 
5015100. 



Contractor's fee/ 5,0 pet of above subtotal 
Section cost 



38449100. 
1922500. 



40371600. 



(1) Equipment costs are based on the M and S index of 749.3, 

(2) Instal 1 ed cost . 



19 



TABLE A-8.-Equi pment cost summary* sulfur dioxide handing section 



Cost (1) 



Item 



Equi pment 



Labor 



Total 



Liquid sulfur storage tank 

Pumps.... • • 

Sulfur furnace............ 

haste-heat boiler .. 

Blowers... 

Absorption tower , 

Pumps. 

Pumps • 

Stripping tower , 

Keboi 1 er •• , 

Pumps , 

Condenser. •• , 

Pumps.. , 

Compressors.. , 

Total ■ 

water chiller • , 



65900. 
1^800. 

9100. 
47400. 
117100. 
41900. 
12600. 
12800. 
27900. 

4600. 

7900. 

66300. 

16300. 

2578000, 



32000. 

1400. 

14300. 

1500. 

700. 

800. 

3200. 

3200. 

500. 

300. 

2200. 

1700. 

3900. 

226-00. 



97900. 

16200. 

23400. 

48900. 

117800. 

42700. 

16000, 

16000. 

28400. 

4900. 

10100. 

68000, 

20200. 

2600800. 



3022800. 



88500. 



(2) 



3111300. 
50900. 



Total equipment cost x factor indicated: 

Foundations/ x .078 

Buildings? x .011 

Structures* x .200.. 

Insulation/ x .031...,..,...,.., 

Instrumentation/ x ,080 

Electrical/ x .228.,, 

Piping/ x .600 

Painting/ x .010 

Miscellaneous/ x .100 

Total 



234800 
34100 

604600 
93300 

241800 

689900 

1813700 

30200 

302300 



4044700 



Total direct cost 



Field indirect/ 10,0 pet of total airect cost 
Total construction cost 



7206900. 



720700. 



Engineering/ 10.0 pet of total construction cost 
Administration and overhead/ 5.0 pet of total 

construction cost.......... , 

Subtotal , 



7927600. 
792800. 
396400. 



Contingency/ 15.0 pet of above subtotal 
Subtotal 



9116800. 
1367500. 



Contractor's fee/ 5,0 pet of above subtotal 
Section cost. 



10484300. 
524200. 



11008500. 



(1) Equipment costs are based on the M and S index of 749.3. 

(2) Instal 1 ed cost • 



20 



TABLE A-9. -Equipment cost summary* caustic digestion section 



Item 



CostCl) 



fcauipment 



Labor 



Total 



Bel t conveyors • 
Hopper. ........ 

Sc rew f eeoer ... 
i^i x i ng tank. ... 

Pumps 

Pu^ps 

heat exchanger. 
Heat exchanger. 
Pumps.......... 

Digestion tanks 
PI ash tank 1 . . . 

tank 

tank 

tank 

tank 

tank 

tank 

tank 

tank 



Fl ash 
Fl ash 
Flash 
Flasn 
Flash 
Fl ash 
F I ash 
Flash 

Pumps. 

Pressure-leaf filters 

Neslurry tanks 

Pumps...... 

Total , 

Slurry storage tank.., 



566700 
5400 
li600 
29400 
22900 
21400 
21000 
27500 

146100 
2747200 
73000 
55800 
U4200 
35000 
33*00 
33^00 
33*00 
33400 
33400 
27900 

356700 
80600 

1014 



. $ 



4545000 



Total equipment cost x factor indicated 

Foundations, x .211 

Buildings, x .041.... 

Structures, x .100 

Insulation, x .017 

Instrumentation, x .180 

Electrical, x .056 , 

Piping, x .700 

Painting, x .080 

Miscellaneous, x .100 

Total..... 



Tota 1 oi rect cost 



Field indirect, 10.0 pet of total direct cost 
Total construction cost 



142600. 

900. 

700. 
5500. 
4300. 
4300. 
1100. 
1300. 
9200. 
4600. 

600. 

800. 

600. 

eoo. 

800. 

eoo. 

800. 

eoo. 

800. 

4200. 

35700. 

24800. 

18800, 



711300. 
6300. 

14300. 

34900. 

27200. 

25700. 

22100, 

26600. 

155300. 

2751800. 

73800. 

56600. 

45000. 

35800. 

34200. 

34200. 

34200. 

34200. 

34200. 

32100. 
392400. 
105600. 
120200. 



265200. 



(2D 



4810200. 
355200. 



958600 
186600 
454500 
79300 
818100 
256300, 
3181500, 
363600, 
454500, 



6753000 



Engineering, 10.0 pet of total construction cost 
Administration and overhead, 5.0 pet of total 

construction cost 

Subtotal 



Contingency, 15,0 pet of above subtotal 
Subtotal 



Contractor's fee, 5,0 pet of above subtotal 
Section cost 



11918400. 
1191800. 



13110200, 

1311000. 

655500. 



15076700. 
2261500. 



17338200. 
866900. 



16205100. 



(1) Equipment costs are based on the H ano S index of 7*9,3. 

(2) Inst al 1 eo cost . 



21 



TABLE. A-lO.-Equi pment cost summary* 
trihydrate precipitation and calcination section 



Item 



Equi pment 



CostCl) 



Labor 



Total 



Pumps..,. 

Precipitation tanks. 
Pumps .............. . 

Primary thickeners.. 

Sumps..... 

Underflow pumps..... 
Secondary thickeners 

Sumps........ 

Underflow pumps 

Tertiary thickeners. 

Sumps...... ,, 

Underflow pumps 

Surge tanks 

Pumps 

Overflow pumps...... 

Surge tanks 

Pumps 

Belt conveyor.. 

Screw feeaers ...... , 

Total 

Air compressors...... 

Fluid-flash calciner, 
Silos....... ..., 



62200. 

1740100. 

226000. 

338300. 

4100. 

29500. 

644400. 

20600. 

52900. 

1578200. 

5700. 

24700. 

29600. 

61600. 

41800. 

25400. 

41800. 

146700. 

32500. 



5106100. 



24U0Q. 

660800. 

62800. 

49900. 

5300. 

5700. 
96800. 
14500. 

9600. 
170500. 

6500. 

5400. 
11800. 
10000. 

9200. 
16400. 

9200. 
28700. 

4900. 



86600. 

2420900. 

288800. 

388200. 

9400. 

35200. 
741200. 

35100. 

62500. 
1748700. 

12200. 

30100. 

41400. 

71600. 

51000. 

41800. 

51000. 
175400. 

37400. 



1222400. 



6328500. 
(2) 223400. 
(2) 6148600. 
(2) 4817300. 



Total equipment cost x factor inaicateo: 

Foundations, x .429. 

buildings* x .025... 

Structures* x .050 

Instrumentation* x ,150 

Electrical* x .087 

Piping* x .400 

Painting* x .050 

Miscellaneous* x .100 

Total 



2191200. 

130100. 

255300. 

765900. 

442100. 
2042400. 

255300. 

510600. 



6592900. 



Total direct cost 



Field indirect* 10.0 pet of total direct cost 
Total construction cost • 



24110700. 
2411100. 



Engineering* 10.0 pet of total construction cost 
Administration ana overhead* 5.0 pet of total 

construction cost 

Subtotal 



26521800. 
2652200. 
1326100. 



Contingency* 15.0 pet of above subtotal 
Subtotal 



30500100. 
4575000. 



Contractor's fee* 5.0 pet of above subtotal 
Sect ion cost 



35075100. 
1753800. 



36828900. 



(1) Equipment costs are based on the M and S index of 749.3. 

(2) Inst al 1 ed cost . 



22 



TABLE A-l 1 .-Equi pment cost summary/ 
Digestion liauor regeneration section 





Cost(l) 


Item 


Equi pment 


Labor 


Total 




$ 3067000, 

1220C. 

23300. 

10 0. 

17600. 

490 0. 

1500. 

490 0. 

234500, 

20 0. 

4900. 

4900. 

65000. 

31000. 

3270 0. 

3940C. 

5360 0. 

56000. 

6 7 0. 

109000. 

1219 0. 

9 79 00. 

101500. 

139300. 

54100. 

415200. 

12100. 

14800. 

1700. 

15300. 

1210 0. 

15300. 

9900. 

23700. 

4900. 

14800. 

4900. 

247800. 

10900. 

36300. 

410 0. 

2200. 

4900. 


$ 300800. 
3100. 
8000. 
2700. 
4100. 
1200. 
1600. 
1200. 
47500. 

400. 

800. 

900. 
23300. 
8700. 
8700. 
1100. 
1400. 
1400. 
1500. 
2300. 
2600. 
1900. 
2C00. 
2400. 
17 0. 
152900. 
8800. 
3900. 
2600. 
3900. 
8800. 
3900. 

50 0. 
8800. 

400. 
1300. 

500. 

129200. 

1600. 

5700. 

1900. 

300. 

900. 


4 3367600. 




15300 . 




31300 , 




12700 . 




217 0. 




6100. 




3100, 




6100 . 




262000 . 




600 . 




5700. 




58 0. 




86300. 
397Cv. 




41 400 . 




40500. 




55200. 




57400, 




62200, 




1 1 1300, 




124500. 




9960 0. 




103500. 




141700, 




71100, 




568100 . 




20900. 
18700. 




4300, 




19200, 




20900. 




19200, 




10400, 




32500. 




53 0. 




1610 0. 




5400. 




377000. 




12500. 




4200C. 




6000, 




2500. 




5600. 




5199100. 


782500. 


5981600 . 




(2) 1643800. 




(2) 55700. 











TAdLE A-l 1 ,-£qui pment cost summary/ 

oigestion liquor regeneration section 

(cont i nued) 



23 



Total equipment cost x factor indicated: 

Foundations/ x .345.. •••....•. 

Buildings, x .015.. 

Structures/ x .050 

Insulation/ x .289... 

Instrumentation/ x .150 

Electrical/ x .032 

Piping/ x .600 •••.. • 

Painting/ x .050 

Miscellaneous/ x .100 

Total 

Total oirect cost.. 

Field indirect/ 10.0 pet of total direct cost... 
Total construction cost... 

Engineering/ 10.0 pet of total construction cost 
Administration and overhead/ 5.0 pet of total 

construction cost..... • 

Subtotal 

Contingency/ 15.0 pet of above subtotal 

Subtotal.... 

Contractor's fee/ 5.0 pet of above subtotal.,.. 
Section cost... • 



1794200 

77500 

260000 

1501300 
779900 
167500 

3119500 
260000 
519900 



8479800 



16160900. 



1616100. 



17777000. 
177770 0. 

888900. 



20443600. 
3066500. 



23510100. 
1175500. 



24685600. 



(1) Equipment costs are based on the M and S index of 749.3. 

(2) Jnstal 1 eo cost . 



24 

















Dust loss 












A1 2 3 

Si0 2 

Ti0 2 

h 2 o ; 

Total 


16 

21 

1 

,652 

,690 








Water 






H 2 




113 














w 






t 






Raw c 


ay 
















Calcined clay 


A1 2 3 
Si0 2 
Fe 2 3 
Ti0 2 
H 2 
Total 


1,571 
2,073 
49 
117 
1,539 
5,349 










A1 2 3 
Si0 2 
Fe 2 3 
Ti0 2 
Total 


1,555 

2,052 

49 

116 

3,772 


SIZE REDUCTION 




MISTING 




CALCINATION 



























FIGURE A-l. - Material balance, clay preparation section (tons per day). 







Recycle 


sulfurojs acid 




H 2 
SO 2 
Total 


8,477 
12,054 
20,531 










1 




Ca 


cined clay 






A1 2 3 
Si0 2 
Fe 2 3 
Ti0 2 
Total 


1,555 

2,052 

49 

116 

3,772 






1 




LEACHING 








^1 


1 














Recycle 


leach solution 




AI2O3 
Si0 2 
Fe 2 3 
H 2 
S0 2 
Total 


27 
14 
18 

17,343 
572 

17,974 



S0 2 from leaching 




Wash 


water 






S0 2 6,187 


H 2 


13,014 




a 




















Pregnant 


iquor 




I 




f 




AI2O3 
Si0 2 
Fe 2 3 
H 2 

S0 2 
Tota 1 


1,068 

20 

45 

36,260 

6,402 

43,795 


FILTRATION 












1 




' 








Leach residue 








A1 2 3 514 
Si0 2 2,046 
Fe 2 3 22 
Ti0 2 116 
H 2 2,574 
S0 2 37 
Total 5,309 





FIGURE A-2. - Material balance, sulfurous acid leaching section (tons per day). 



S0 2 from precipitation 




S0 2 3,850 




J 


i 






PRECIPITATION 




THICKENING 




i 


1 




J 


Pregnant liquor 




Recycle leach solution 


A1 2 3 1,068 
Si0 2 20 
Fe 2 3 45 
H 2 36,260 
S0 2 6,402 
Total 43,795 


A1 2 3 27 
Si0 2 14 
Fe 2 3 18 
H 2 17,343 
S0 2 572 
Total 17,974 



Oxygen 



28 



DECOMPOSITION 



Decomposi 


tion 


vap 


or 


H 2 
S0 2 
Total 




9 
1 

11 


,916 
912 
,828 



-Oxygen shown entering is assumed to 
have dissolved in the system and 
oxidized some sulfites to sulfates. 



FILTRATION 




Waste 


so 


ution 


Si0 2 




1 


Fe 2 3 




10 


H 2 




5,970 


so 2 




14 


Total 




5,995 



FIGURE A-3. - Material balance, sulfite precipitation and decomposition section (tons per day). 



25 



Absorption water 



H,0 



5,300 



Air 



2 
N 2 



106 
352 
"555 





S0 2 from precipitation 




S0 2 from leaching 




S0 2 3,850 


S0 2 6,187 
















Decomposition vapor 




1 




u n Q QIC 








■ 




SO 2 


1,912 




CONDENSATION 


* » 


COMPRESSION 


Total 


11,828 




li 






w 






v 




Condensate 






Recycle sulfurous acid 




H 2 1,440 


H 2 8,477 

S0 2 12,054 

Total 20,531 










Stripped air 








2 53 

N 2 352 

H 2 5 

Total 410 




i 


1 










ABSORPTION 




STRIPPING 








i 


i 




" 












Stripping wastes 




SULFUR BURNING 




Elemental sulfur 




H 2 5,294 






S0 2 
Total 


1 












5,295 





FIGURE A-4. - Material balance, sulfur dioxide handling section (tons per day). 



Alumina monohydrate 



A1 2 3 
Si0 2 
Fe 2 3 
SOi, 
H 2 
Total 



1,041 

5 

17 

82 

3,031 

4,176 



H,0 



Steam 



1,444 



DIGESTION 
1 



Caustic leach solution 



A1 2 3 
Na 2 
H 2 
C0 2 
CaO 
Total 



1,006 

2,601 

7,922 

572 

12,126 



Recovered 


stean 




275 psig 




305 


225 psig 




264 


175 ps ig 




301 


100 psig 




545 


50 psig 




549 


30 psig 




302 


15 psig 




278 


5 psig 




267 


ps ig 




180 


Total 


2 


,991 



FLASH COOLING 



H,0 



Wash water 



1,200 



FILTRATION 



Digestion residue 



A1 2 3 
Si0 2 , 
Fe 2 3 
Na 2 
C0 2 
CaO 
H 2 
Total 



31 

5 

17 

3 

21 

25 

97 

199 



Pregnant solution 



A1 2 3 
Na 2 
H 2 
C0 2 
SO,, 
Total 



2,016 

2,598 

10,509 

551 

82 



15,756 



FIGURE A-5. - Material balance, caustic digestion section (tons per day). 



26 









Carbon dioxide 






Wash water 




C0 2 * 


22 


H 2 1 


,010 














H 




Pregnant 


solution 








A1 2 3 
Na 2 
H 2 
C0 2 
SO,, 
Total 


2,016 

2,598 

10,509 

551 

82 

15,756 




V 












PRECIPITATION 




PRIMARY THICKENING 


FILTRATION 
AND WASHING 








l 


1 


















i 


[_ 














' 










SECONDARY THICKENING 
















1 








TERTIARY THICKENING 






' 





















Dust loss 


A1 2 3 


10 


C0 2 


1 


H 2 


731 


Total 


742 


l\ 


CALCINATION 


1 1 


Alumina 


A1 2 3 1 


,000 


Na 2 


5 


H 2 


5 


SO,, 


82 


Total 1 


,092 



V 


Recycle caustic 


solution 


A1 2 3 1,006 


Na 2 2,593 


H 2 10,783 


C0 2 572 


Total 14,954 



-Carbon d i ox i de shown entering here is assumed 
to have dissolved in the system and converted 
some sodium hydroxide to sodium carbonate . 



FIGURE A-6. - Material balance, trihydrate precipitation and calcination section (tons per day). 





Water vapor 














H 2 2 


870 






Recycle caustic 
solution 




I 


I 








Caustic leach 
solution 


A1 2 3 1,006 
Na 2 2,593 
H 2 10,783 
C0 2 572 
Total 14,954 


A1 2 3 1,006 
Na 2 2,601 
H 2 7,922 
C0 2 572 
CaO 25 
Total 12,126 




EVAPORATION 








♦ ] 


I 












! 










J 
















Makeup r 


eagents 








CaO 
Na 2 
H 2 
Total 




25 
8 
9 

42 





FIGURE A-7. - Material balance, digestion liquor regeneration section (tons per day). 



INT.-BU.OF MINES, PGH., PA. 27229 



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